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Bistability of Hydrogen Impurity in ZnO under Light Illumination

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Key Laboratory of Inorganic Functional Material and Device, CAS, Shanghai Institute of Ceramics, Chinese Academy of Sciences 

中国科学院无机功能材料与器件重点实验室

  Bistability of Hydrogen Impurity in ZnO under Light Illumination 

  Prof. Chul-Hong Park 

  Research Center for Dielectric and Advanced Matter Physics, Department of Physics Education, 

  Pusan National University 

  时间:2015年04月23日(星期四)上午09:00 

  地点: 4号楼14楼 第一会议室 

  联系人:曾江涛 副研究员 

  李国荣 研究员 

  欢迎各位老师同学光临!

  Bistability of Hydrogen Impurity in ZnO under Light Illumination 

  Chul Hong Park 

  1Research Center for Dielectric and Advanced Matter Physics, Pusan National University, Gumjung, Busan 609-735, Korea 

  Since ZnO-based oxide semiconductors are promising materials for transparent oxide electronics and blue LED, the oxides have been extensively investigated. The heavily n-type doping of ZnO is now intensively investigated for the application of the transparent conducting oxide for the solar cell. Hydrogen is an ubiquitous element, and in semiconductors, hydrogen-related problems have always been important subjects, since hydrogen shows complicated properties. Substitutional hydrogen at oxygen site (HO) is well-known to be a robust source of n-type conductivity in ZnO, but a puzzling aspect is that the doping limit by hydrogen is only about 1018cm-3, even if solubility limit is much higher.

  There is another puzzling aspect in ZnO, which is persistent photo-conductivity (PPC) in Zn. Since the PPC is a source of the light-induced instability of ZnO-based active device in flat panel display, it prevents the wide applications of theZnO-based thin film transistor, andmany researches are now invested to prevent it, however up to now, there is no satisfactory theory about two puzzles. We report the bistability of HO in ZnO through first-principles electronic structure calculations. We find that as Fermi level is close to conduction bands, the HO can undergo a large lattice relaxation, through which a deep level can be induced, capturing electrons and the deep state can be transformed into shallow donor state by a photon absorption. We suggest that the bistability can give explanations to two puzzling aspects.

  Ref) H-H Nahm, C. H. Park, Y-S Kim - Scientific reports,4, 412 (2014)

 
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